Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932250Ab3CKVZm (ORCPT ); Mon, 11 Mar 2013 17:25:42 -0400 Received: from fieldses.org ([174.143.236.118]:53070 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754702Ab3CKVZk (ORCPT ); Mon, 11 Mar 2013 17:25:40 -0400 Date: Mon, 11 Mar 2013 17:25:35 -0400 From: "J. Bruce Fields" To: Tim Gardner Cc: linux-kernel@vger.kernel.org, Trond Myklebust , "David S. Miller" , Tom Tucker , Haggai Eran , Or Gerlitz , Shani Michaeli , linux-nfs@vger.kernel.org, netdev@vger.kernel.org Subject: Re: [PATCH linux-next v3] SUNRPC: rpcrdma_register_default_external: Dynamically allocate ib_phys_buf Message-ID: <20130311212535.GG642@fieldses.org> References: <4FA345DA4F4AE44899BD2B03EEEC2FA9286BA156@sacexcmbx05-prd.hq.netapp.com> <1363036508-24935-1-git-send-email-tim.gardner@canonical.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1363036508-24935-1-git-send-email-tim.gardner@canonical.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4899 Lines: 122 On Mon, Mar 11, 2013 at 03:15:08PM -0600, Tim Gardner wrote: > rpcrdma_register_default_external() is several frames into the call stack which > goes deeper yet. You run the risk of stack corruption by declaring such a large > automatic variable, so move the array of 'struct ib_phys_buf' objects into the > transport structure 'struct rpcrdma_xprt' (which is dynamically allocated) in > order to silence the frame-larger-than warning. Access to each struct > rpcrdma_xprt is serialized by XPRT_LOCKED in xprt_reserve_xprt(), so there is > no danger of multiple accessors to the array of struct ib_phys_buf objects. > > net/sunrpc/xprtrdma/verbs.c: In function 'rpcrdma_register_default_external': > net/sunrpc/xprtrdma/verbs.c:1774:1: warning: the frame size of 1056 bytes is larger than 1024 bytes [-Wframe-larger-than=] > > gcc version 4.6.3 > > Cc: Trond Myklebust > Cc: "J. Bruce Fields" > Cc: "David S. Miller" > Cc: Tom Tucker > Cc: Haggai Eran > Cc: Or Gerlitz > Cc: Shani Michaeli > Cc: linux-nfs@vger.kernel.org > Cc: netdev@vger.kernel.org > Signed-off-by: Tim Gardner > --- > v1 - Use kmalloc() to dynamically allocate and free the array of 'struct > ib_phys_buf' objects > > v2 - Move the array of 'struct ib_phys_buf' objects into struct rpcrdma_req > and pass this request down through rpcrdma_register_external() and > rpcrdma_register_default_external(). This is less overhead then using > kmalloc() and requires no extra error checking as the allocation burden is > shifted to the transport client. > > v3 - Move the array of 'struct ib_phys_buf' objects into struct rpcrdma_xprt. > Pass a pointer to this transport structure into rpcrdma_register_default_external(). > This is less overhead then using kmalloc() and requires no extra error checking > as the allocation burden is shifted to the transport client. Looks good to me; wish we could get it tested.... In future if we do decide to also increase the size of that array we may need to allocate it separately from struct rpcrdma_xprt itself, which looks already fairly large without it; on x86_64: $ gdb net/sunrpc/xprtrdma/xprtrdma.ko ... (gdb) p sizeof(struct rpcrdma_xprt) $1 = 2912 But that shouldn't be a big deal to do. --b. > > net/sunrpc/xprtrdma/verbs.c | 10 ++++++---- > net/sunrpc/xprtrdma/xprt_rdma.h | 5 ++++- > 2 files changed, 10 insertions(+), 5 deletions(-) > > diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c > index 93726560..c7aa3da 100644 > --- a/net/sunrpc/xprtrdma/verbs.c > +++ b/net/sunrpc/xprtrdma/verbs.c > @@ -1730,13 +1730,14 @@ rpcrdma_deregister_memwin_external(struct rpcrdma_mr_seg *seg, > } > > static int > -rpcrdma_register_default_external(struct rpcrdma_mr_seg *seg, > - int *nsegs, int writing, struct rpcrdma_ia *ia) > +rpcrdma_register_default_external(struct rpcrdma_xprt *r_xprt, > + struct rpcrdma_mr_seg *seg, int *nsegs, int writing, > + struct rpcrdma_ia *ia) > { > int mem_priv = (writing ? IB_ACCESS_REMOTE_WRITE : > IB_ACCESS_REMOTE_READ); > struct rpcrdma_mr_seg *seg1 = seg; > - struct ib_phys_buf ipb[RPCRDMA_MAX_DATA_SEGS]; > + struct ib_phys_buf *ipb = r_xprt->ipb; > int len, i, rc = 0; > > if (*nsegs > RPCRDMA_MAX_DATA_SEGS) > @@ -1827,7 +1828,8 @@ rpcrdma_register_external(struct rpcrdma_mr_seg *seg, > > /* Default registration each time */ > default: > - rc = rpcrdma_register_default_external(seg, &nsegs, writing, ia); > + rc = rpcrdma_register_default_external(r_xprt, seg, &nsegs, > + writing, ia); > break; > } > if (rc) > diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h > index cc1445d..d7b440f 100644 > --- a/net/sunrpc/xprtrdma/xprt_rdma.h > +++ b/net/sunrpc/xprtrdma/xprt_rdma.h > @@ -269,7 +269,8 @@ struct rpcrdma_stats { > * for convenience. This structure need not be visible externally. > * > * It is allocated and initialized during mount, and released > - * during unmount. > + * during unmount. Access to this structure is serialized by XPRT_LOCKED > + * in xprt_reserve_xprt(). > */ > struct rpcrdma_xprt { > struct rpc_xprt xprt; > @@ -279,6 +280,8 @@ struct rpcrdma_xprt { > struct rpcrdma_create_data_internal rx_data; > struct delayed_work rdma_connect; > struct rpcrdma_stats rx_stats; > + /* temp work array */ > + struct ib_phys_buf ipb[RPCRDMA_MAX_DATA_SEGS]; > }; > > #define rpcx_to_rdmax(x) container_of(x, struct rpcrdma_xprt, xprt) > -- > 1.7.9.5 > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/